WBC is the abbreviation of white blood cell, which is a kind of blood cell. According to the presence or absence of special granules in the cytoplasm of leukocytes, they can be divided into granulocytes and agranulocytes, and according to the staining characteristics of special granules, they are divided into neutrophils, basophils and eosinophils. Leukocytes are often referred to as immune cells. Under a microscope, you can see that the larger and less numerous blood cells with a nucleus are leukocytes, whose main function is to engulf germs and defend against disease. The number of leukocytes in a normal person ranges from 4,000 to 10,000/mL; if it is lower than 4,000/mL, it is called leukopenia, and if it is higher than 10,000/mL, it is called leukocytosis.